The subject matter of the present invention relates generally to apparatus for measuirng the moisture content of particulate material in a moving particulate layer carried on a conveyor by transmitting a beam of microwave radiation through such layer so that a portion of such beam is absorbed by such moisture. More particularly, the invention relates to such an apparatus employing an improved leveling means for leveling the thickness of the particulate layer prior to measurement of the moisture content. Preferably, the leveling means of the present invention includes a rotating endless, flexible leveling belt and a pressure roller which urges the leveling belt into contact with the top surface of the layer of particulate material to level such surface laterally across the layer. The height of the pressure roller and leveling belt above the conveyor may be adjusted in response to changes in the thickness longitudinally along the particulate layer. A beam of penetrating radiation diverse from microwaves, such as gamma radiation, which is absorbed by the total mass of the particulate material may also be transmitted through the measured portion of the particulate layer in order to determine the mass of such layer so that the percent of moisture content may be calculated. The source or detector of the microwaves and/or penetrating radiation may be positioned within the leveling belt to provide a more compact measurement apparatus.
Previously it has been proposed in U.S. Pat. No. 3,460,030 issued Aug. 5, 1969 to Brunton et al and my earlier U.S. Pat. No. 3,693,079 issued Sept. 19, 1972 to Walker to provide an apparatus for measuring the percent moisture content of particulate material using beams of microwaves and penetrating radiation, including gamma rays. However, these prior art apparatus were not completely successful because of their inability to maintain the measured particulate layer with a sufficiently uniform predetermined thickness. Thus, the leveling rake means and the leveling roller means of U.S. Pat. No. 3,693,079 have not proved satisfactory in leveling the particulate layer for certain applications of such apparatus because they do not contact a sufficiently large area of such layer.